The present invention relates to relay antenna masts for cellular radio telecommunications systems.
Conventionally, in urban areas, relay antenna masts are installed on high sites such as the tops of buildings, and they can be located at heights of up to 40 meters, or even more.
It is necessary to be able to work regularly on the antennas carried by such masts, in order to perform maintenance and also to adjust their pointing in elevation and in azimuth.
Because of the height of antennas on a mast, and because of the need to have access to the antennas, operatives are frequently exposed to the danger of falling.
For reasons associated particularly with questions of size and appearance, it is difficult to envisage providing guard rails extending up the full height of such masts so as to make it quite safe to work on them.
There thus exists a need for a solution capable of ensuring that work on antennas installed at the ends of such masts is made quite safe.
Radio amateur antenna masts are already known which are of the tilting type. In this respect, reference can be made in particular to U.S. Pat. No. 4,167,740.
Nevertheless, radio amateur antennas constitute a technical field which is different from that of antennas for cellular communications.
The invention provides an antenna mast enabling the above requirements to be satisfied.
The solution proposed by the invention presents the advantage of being particularly simple, of not requiring maintenance, of being adapted to being installed out of doors, and to withstanding bad weather.
Because of its simplicity, intensive use does not lead to abnormal wear.
Furthermore, operatives no longer need to climb to the top of the masts to work on the antennas, so it is no longer necessary to provide steps or anchor points up the masts, and the equipment required by operatives is greatly simplified (no harness, tethers, etc.). Furthermore, the absence of steps on the mast means that it fits in well with its environment.
The solution proposed by the invention is a relay antenna mast for a cellular radio telecommunications system, the mast being characterized in that it comprises:
a mast stand;
at least one arm pivotally mounted on said mast stand and carrying at least one antenna; and
means for locking said arm in a position in which the antenna(s) is/are in a high position;
said arm being suitable, when said locking means are disengaged, for being tilted about its pivot axis to a position in which at least one antenna is at a height enabling it to be worked on by an operative at the foot of the mast.
Such a mast is also advantageously associated with the various characteristics below taken singly or in any technically feasible combination:
in a first variant, the arm extends on either side of its pivot axis and carries counterweight-forming means on its branch opposite from its branch carrying the antenna(s);
the counterweight-forming means are adjustable in mass and/or in translation along the arm;
in another variant, it includes a linkage comprising two elements fixed one to the mast stand and the other to the arm, one of the elements carrying means for fixing a retaining device enabling the operative to control tilting of the arm;
the retaining device is a removable device put into place by the operative prior to releasing the locking means, and subsequently removed once the locking means have been re-engaged after work has been carried out;
it comprises a plurality of arms pivotally mounted on a common mast stand; and
an arm carries a plurality of antennas.
The invention also provides a platform for a relay antenna mast in a cellular radio telecommunications system for use in an urban area, the platform comprising a relay antenna mast and a protective guard rail, and being characterized in that the antenna mast is a mast of the above-specified type.
In particular, the antenna mast and the guard rail are carried on the top of a building.
The invention also provides the use of a tilting antenna mast to carry at least one relay antenna in a cellular radio telecommunications system.